Production of textile and other articles from acrylonitrile polymers



United States Patent PRODUCTION OF TEXTILE AND OTHER ARTI- CLES FROM ACRYLQNITRILEE POLYMERS John Downing and James Gordon Napier Drewitt, Spondon, near Derby, England, assignors to British Celanese Limited, a corporation of Great Britain No Drawing. Application November 19, 1951, Serial No. 257,198

Claims priority, application Great Britain December 5, 1950 9 Claims. (Cl. 18-54) This invention relates to the production of textile and other shaped articles, such for example as filaments and films, from solutions of polyacrylonitrile or of a copolymer containing acrylonitrile as the preponderating constituent.

According to the invention, a solution or a fibreforming polyacrylonitrile or copolymer containing a preponderating proportion ofacrylonitrile is shaped, as by extrusion or casting, and is coagulated by means of a liquid carboxylic ester of boiling point above 250 C.

The invention is of particular importance in the production of shaped articles from polyacrylonitrile itself, and will be described with particular reference to polyacrylonitrile. It is, however, also of value in connection with copolymers, especially copolymers of acrylonitrile and another vinyl compound or compounds in which acr'ylonitrile is the preponderating constituent, and especially in which the proportion of acrylonitrile exceeds 85%. Examples of vinyl compounds which may be copolymerised with acrylonitrile are methacrylonitrile, vinyl chloride, vinyl acetate, acrylic acid esters such as methyland phenyl acrylate, styrene and its derivatives, and vinylidene chloride. For the sake of brevity, the term acrylonitrile polymers will be employed. to denote both polyacrylonitrile itself and copolymers in which acrylonitrile preponderates.

Examples of the esters that may be used as coagulating liquids are di-methyl phthalate, di-ethyl phthalate, di-nbutyl phthalate, di-isobut-yl phthalate, di amyl phthalate, di-hexyl phthalate, di-(Z-ethyl-n-hexyl) and di-n-octyl phthalates, di-(Z-methoxyethyl) phthalate, di-(Z-butoxyethyl) .phthalate, di-n-butyl sebacate, tri-ethyl and trin-butyl citrates, di-n-butyl tartrate, triacetin, amyl benzoate and 1:3-buty1ene glycol dibenzoate. (The commercial products, which in some cases are mixtures of isomers, may be used.) We prefer to use esters con taining at least two carboxylate groups in the molecule, and we have found that dialkyl esters of dicarboxylic acids and especially dialkyl phthalates are particularly useful. It is not necessary, though it will usually be convenient, that both or all the carboxylate groups in such esters should be identical; mixed esters can be used.

The use of high boiling esters as coagulating liquids in accordance with the invention is most valuable in conjunction with spinning solutions in which the acrylonitrile polymer is dissolved in a solvent mixture having nitromethane as its principal constituent. Such solvent mixtures are described in U. S. application S. Nos. 231,662, now abandoned, 231,663, and 231,664, all filed June 1-4, 1951, and in British specification. No. 14,388/51, all of A. Hodge, LDowning and J. G. N. Drewitt, and U. 18. Patent No. 2,679,492. Particularly good results are obtained when the spinning solution consists of polyacrylonitrile, or a copolymer containing at least 85% of acrylonitrile, dissolved (a) in a homogeneous mixture of nitromethane and water containing at least 6% by weight of water but less water than nitromethane,

as described in U. S. application S. No. 231,662, or (b) in a mixture of nitromethane and formic acid, with or without water, containing about 5090% by weight of nitromethane, or (c) in a mixture of nitrornethane and resorcinol or catechol, with or without water, in which the proportion of nitromethane is about -90% by weight, and that of resorcinol or catechol at least 5% by weight, as described in U. S. Patent No. 2,679,492 corresponding to British application No. 29,772/50. Other solutions of the polymers may however be coagulated by means of the high boiling carboxylic esters, e. g. solutions in dimethyl formamide, lactones such as propiolact-one, butyrolactone or a valerolactone, mor p-nitrobenzene, sulpholane, nitroethanol or a nitropropanol (as described in U. S. application S. No. 202,399, filed December 22, 1950, of 1. Lincoln), a cyanhydrin such as ethylene cyanhydrin, or compositions comprising dior polyhydric phenols but not nitromethane, such as are described in U. S. application S. No. 272,517 of E. J. Kowolik, 3. Downing and J. G. N. Drewitt, now Patent No. 2,706,185.

The acrylonitrile polymer preferably has a viscosity between 2.5 and 4 centistokes and especially between 2.5 and 3.5 centistokes. (Here and throughout the specification the viscosities of the polymers are expressed in terms of the viscosity of a 1% solution of the polymer in dimethyl formamicle at 20 C.) The concentration of the solution to be extruded or cast may be between 7.5% and 20%, and its temperature should be kept sufficiently high to ensure that the polymer does not begin to separate before the extrusion or casting. Moreover the temperature of the solution betcre extrusion or casting should be so correlated with the concentration and with the viscosity of the polymer that the solution has a satisfactory spinning or casting viscosity. For example, a 15% solution of a poiyacrylonitrile of viscosity 2.6 centistokes in a mixture of about 90% of nitromethane and 25l0% or resorcinol may be at a temperature between 25 and 50 C. Other solutions may require higher temperatures. The coagulating liquid may be at or below room temperature, e. g. at l0-20 C., or at a higher temperature; preferably it is at a temperature above 50 (1., e. g. about 5595 C. when the spinning solution comprises nitromethane as the principal constituent.

The invention may be applied to the manufacture of films, foils and the like by extrusion or casting methods, but it is particularly important in connection with the manufacture of filaments from the acryl-onitrile polymers. (The term filaments is employed to denote filamentary material in general, for example multi-filament twisted and untwisted yarns, two, and single continuous filaments of high denier.) Such filaments may be made by extruding a solution of the polymer through appropriate orifices horizontally or vertically or at an angle to the horizontal into a bath of the coagulating liquid, and the coagulating liquid may be caused to flow in the same direction, or in the opposite direction, or more or less transversely to the direction of travel of the filaments, or it may be relatively quiescent.

Filaments, films and the like made in accordance with the invention may be subjected to subsequent setting,- stretching and relaxing operations such as are known for 'polyacrylonitrile articles made by other methods.

For example, they may be stretched in hot water, e. g.

water at a temperature between and C., or while softened by dry heat, e. g. while passing over a heated metal surface at a temperature of about l2 0=-l60 C. For example filaments may be stretched to about 37 times their original length.

The stretched filaments and films may be relaxed in order to increase their extensibility, for example by heating them to about 140-200 C. in the absence of tension or under a tension insuflicient to prevent them shrinking. Moreover filaments and films made in ac cordance with the invention, whether or not they have been stretched, may be set by heating them to a temperature between 100 and 160 C. while they are held at constant length, in order to increase their dimensional stability. For example filaments may be heated while passing round a thread-storage thread-advancing reel or like device.

After leaving the coagulating bath the filaments or films may be given any suitable treatment to remove coagulating liquid which they have carried away from the bath. For example they may be passed over guides by means of which part of the adherent liquid may be wiped off, after which they may be Washed with a liquid which is a solvent for the high boiling carboxylic ester but not for the acrylonitrile polymer. For example polyacrylonitrile filaments and films may be washed with acetone or petroleum ether. When the filaments or films are to be stretched it is preferable to postpone the wash to some stage subsequent to the stretching operation.

The following examples illustrate the invention.

Example I Polyacrylonitrile of viscosity about 3.3 centistokes was heated with nitromethane to 95 C., and sufficient water was then mixed in to give a mixture comprising 9 volumes of nitromethane to 1 volume of water. The solution of polyacrylonitrile so obtained was cooled to 85 C. and extruded in the form of filaments into a coagulating bath of di-n-butyl phthalate at about the same temperature. The filaments produced were at once stretched to about 6 times their length while passing over a metal plate heated to 140 C., after which they' were heated at constant length to 110 C. for about 30 minutes. Finally they were washed with acetone until they were substantially free from adherent dibutyl phthalate. The product had a good tenactiy and good dimensional stability.

Example 11 The process of Example I was repeated, except that the polyacrylonitrile was dissolved in a solvent mixture of 80 parts by weight of nitromethane, parts by weight of resorcinol and 10 parts by weight of water by heating it with the solvent mixture to about 110 C. in a closed vessel.

Example III A 15% solution of polyacrylonitrile in a mixture of nitromethane and resorcinol containing 77.5% by weight of nitromethane and 22.5% of resorcinol was extruded at 30 C. into a bath of di-n-butyl phthalate at 85 C. and the yarn produced was wound up without washing. The yarn was subsequently stretched by about 6 times its length while passing through a narrow tube in which it was heated to 155 C., and was then thoroughly washed with petroleum ether.

While the processes described in the examples use as coagulating liquid di-n-butyl phthalate, it will be understood that this can be replaced by other high boiling esters as described above. Similarly the polyacrylonitrile can be replaced by another of the acrylonitrile polymers, especially a fibre-forming copolymer of acrylonitrile with vinyl acetate or vinyl chloride containing 8595% of acrylonitrile. While the examples deal with the production of filaments, similar conditions can be used for the production of films or foils using appropriate extrusion or casting devices.

Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the manufacture of shaped articles havtwo polymerizable vinyl monomers, one of which is acrylonitrile, and in which the proportion of acrylonitrile is at least by weight, which comprises shaping a solution of the polymer in a solvent which is at least predominantly organic in nature, and coagulating the shaped solution by means of a liquid di-alkyl phthalate.

2. Process for the manufactureof shaped articles having a basis of a polymer which is derived from at most two polymerizable vinyl monomers, one of which is acrylonitrile, and in which the proportion of acrylonitrile is at least 85% by weight, which comprises shaping a solution of the polymer in a solvent mixture therefor of which at least 50% by weight consists of nitromethane and coagulating it by means of a liquid dialkyl phthalate.

3. Process according to claim 2, wherein the coagulating liquid is at a temperature above 50 C.

4. Process for the manfacture of shaped articles having a basis of polyacrylonitrile, which comprises shaping a solution of the polyacrylonitrile in a homogeneous mixture of nitromethane and water containing at least 6% of water but less water than nitromethane, and coagulating the shaped solution by means of a liquid dicarboxylic acid dialkyl ester of boiling point above 250 C. at a temperature above 50 C.

5. Process for the manufacture of shaped articles having a basis of polyacrylonitrile, which comprises shaping a solution of the polyacrylonitrile in a homogeneous mixture of nitromethane and water containing at least 6% of water but less water than nitromethane, and coagulating the shaped solution by means of a liquid dialkyl phthalate at a temperature above 50 C.

6. Process for the manufacture of shaped articles having a basis of polyacrylonitrile, which comprises shaping a solution of the polyacrylonitrile in a mixture of nitromethane and a dihydroxy benzene unsymmetrical about the center of the benzene nucleus containing 70-90% by weight of nitromethane, and coagulating the shaped solution by means of a liquid dialkyl phthalate at a temperature above 50 C.

7. Process for the manufacture of shaped articles having a basis of polyacrylonitrile, which comprises shaping a solution of the polyacrylonitrile in a mixture of nitromethane, water and a dihydroxy benzene unsymmetrical about the center of the benzene nucleus containing 70-90% by weight of nitromethane and at least 5% by Weight of the dihydroxy benzene, and coagulating the shaped solution by means of a liquid dialkyl phthalate at a temperature above 50 C.

8. Process for the manufacture of shaped articles having a basis of polyacrylonitrile, which comprises shaping a solution of the polyacrylonitrile in a mixture of nitromethane and formic acid containing 50-90% by weight of nitromethane, and coagulating the shaped solution by means of a liquid dialkyl phthalate at a temperature above 50 C.

9. Process for the manufacture of shaped articles having a basis of polyacrylonitrile, which comprises shaping a solution of the polyacrylonitrile in a mixture of nitromethane, formic acid and water containing 5090% by weight of nitromethane, and coagulating the shaped solution by means of a liquid dialkyl phthalate at a temperature above 50 C.

References Cited in the file of this patent UNITED STATES PATENTS 2,210,771 Myles et al. Aug. 6, 1940 2,273,891 Pollack et al Feb. 24, 1942 2,426,728 DAlelio Sept. 2, 1947 2,570,237 Hooper et al. Oct. 9, 1951 

1. PROCESS FOR THE MANUFACTURE OF SHAPED ARTICLES HAVING A BASIS OF A POLYMER WHICH IS DERIVED FROM AT MOST TWO POLYMERIZABLE VINYL MONOMERS, ONE OF WHICH IS ACRYLONITRILE, AND IN WHICH THE PROPORTION OF ACRYLONITRILE IS AT LEAST 85% BY WEIGHT, WHICH COMPRISES SHAPING A SOLUTION OF THE POLYMER IN A SOLVENT WHICH IS AT LEAST PREDOMINANTLY ORGANIC IN NATURE, AND COAGULATING THE SHAPED SOLUTION BY MEANS OF A LIQUID DI-ALKYL PHTHALATE. 